Your email address looks to be a general purpose one (i.e. one that you would use for all your correspondence) so getting Spam shortly after using it on a site does not necessarily indicate that the site is compromised: correlation is not causation. I'm pretty sure my system is secure as such things can be. phpBB is used by hundreds of thousands of people around the world and has shown itself to be pretty solid. I'm not dismissing your warning out of hand though. I'll try seeding the user list with some new accounts with unique email addresses and see if they attract any Spam and let you know the results.

i've been a user of this board since 2007 and a too use a special mailadress, only for this forum. (and a special emailadress for each other forum.call me paranoid, but thats the only option (for me) to check, if spam arrives, from where it came from).

as far as i can tell (i use a spamfilter software only in my thunderbird installation) i never have received any spam from this board, nor from any other phpBB board. hopefully this will not and never change